Exemplary navigation systems provide navigation solutions including position, velocity, and/or attitude data of objects, including aircraft and other vehicles. Some navigation solutions are based on data from inertial sensors, such as accelerometers measuring linear velocity and gyroscopes measuring angular rates. Accelerometers and gyroscopes inherently have errors. These errors build up over time. In order to correct for errors in a navigation solution caused by errors in the accelerometer and/or gyroscope data, aiding sources (aiding devices) can be used. One aiding source that is currently used is a GNSS receiver. When a GNSS receiver is used as an aiding source, navigation systems can blend data received from the GNSS receiver with the navigation solution using a Kalman filter. This GNSS solution has fairly accurate data over a long period, but it is also fairly noisy. Blending together our inertial navigation solution with the GNSS data works well at removing inertial errors.
Exemplary navigation systems also often include feedback of the navigation solution back to the GNSS receiver to aid in tracking. When these navigation systems already have a navigation solution and then subsequently receive a GNSS signal once the GNSS signal is acquired, these navigation systems could have significant error in the navigation solution. When these navigation systems receive initial data from the GNSS receiver, these navigation systems will reset their navigation solution based on the received data fairly quickly. The GNSS signal may not acquire signals until the vehicle is moving and sometimes not even until in the air with the case of aircraft. The GNSS receiver will acquire signals and will start providing data to use in the Kalman filter. Once the initial data is provided by the GNSS receiver for use in the Kalman filter, the navigation solution is reset. The navigation solution is fed back to the GNSS receiver and the GNSS receiver could see a significant reset in its velocities, positions, etc. Because of the high bandwidth of GNSS receivers (and other aiding devices), the loops inside the GNSS receiver could lose track due these step changes in the navigation solution. If the loops within the GNSS receiver lose track, the GNSS data is no longer good and the data would be rejected. In exemplary embodiments, the satellite signal tracking loops inside the GNSS receiver could lose lock with jumps in position that are greater than about 30 meters and/or step changes in velocity that are greater than about 5-10 meters per second. In other embodiments, the loops inside the aiding device could lose lock with greater or smaller changes based on different sensitivities to step changes in the information fed back to the aiding device.